Transthoracic Electrical Bioimpedance Research Articles

The cardiovascular effects of oral nifedipine and nicardipine: A double-blind comparison in healthy volunteers using transthoracic bioimpedance cardiography

The cardiovascular effects of single oral doses of nifedipine (5 and 10 mg) and nicardipine (20 and 30 mg) were compared in a placebo controlled double-blind crossover study involving 8 healthy male volunteers. Two hours following drug administration stroke volume and cardiac index were measured non-invasively using transthoracic electrical bioimpedance cardiography during passive tilting, graded bicycle exercise, and recovery from exercise. Two separate experiments were performed in the absence of active drug to allow the reproducibility of the measurements to be assessed. Coefficients of variation (within experiment/between experiments) for cardiac index were 7.0%/19.9% at rest and 11.5%/9.3% at 180 W exercise. Both nifedipine and nicardipine increased stroke volume and cardiac index and reduced total peripheral resistance (mean blood pressure/cardiac index) at all times in the experiment. Reductions in peripheral resistance were similar for nifedipine 10 mg and nicardipine 20 mg but in these doses slightly larger increases in heart rate were produced by nifedipine, and in stroke volume and cardiac index with nicardipine. The study shows that the cardiovascular effects of nifedipine and nicardipine can be detected using impedance cardiography which is a simple, safe, and inexpensive technique. The differences between the effects of the two drugs were small. Although some were of statistical significance and are consistent with a less marked cardiodepressant effect for nicardipine, the clinical importance of these observations is uncertain. Further studies to examine the effect of oral nifedipine and nicardipine in patients with impaired ventricular function may be helpful in clarifying this tissue.

The use of transthoracic electrical bioimpedance in assessing thoracic fluid status in emergency department patients

Baseline transthoracic electrical bioimpedance (Z) was measured in 26 serlously ill emergency department (ED) patients in order to determine the usefulness of this noninvasive method of assessing thoracic fluid (TF) status. Patients were divided, on the basis of clinical and radiographic information, into three groups: group A (11 patients), with clinically normal TF status; group B (12 patients), with elevated TF status; and group C (3 patients), with decreased TF status. The mean Z values measured in each group were: 26.5 ohms in group A, 21.8 ohms in group B, and 37.4 ohms in group C (differences significant at P < .02). Using a cutoff Z value of 24.0 ohms would have predicted group B individuals with a sensitivity of 92% and a specificity of 79%. In eleven patients, impedance measurement would have added information that confirmed diagnostic suspicions or suggested the diagnosis earlier than would otherwise have occurred. In five patients, real-time changes in Z were potentially useful in guiding and monitoring the results of therapeutic interventions or changes in clinical condition. This study demonstrates that Z measurement and real-time monitoring can be a useful and non-invasive means of assessing TF status in ED patients. However, it may be most helpful in those patients whose TF status is changing or unstable